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Subject: Re: [PATCH] ima: optimize ima_pcr_extend function by asynchronous
To:     Ken Goldman <kgold@linux.ibm.com>, zohar@linux.ibm.com,
        dmitry.kasatkin@gmail.com, jmorris@namei.org, serge@hallyn.com,
        zhangliguang@linux.alibaba.com, zhang.jia@linux.alibaba.com
Cc:     linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200414115020.99288-1-tianjia.zhang@linux.alibaba.com>
 <0fdd1c13-51c6-e65c-1ca5-38621fa21f53@linux.ibm.com>
From:   Tianjia Zhang <tianjia.zhang@linux.alibaba.com>
Message-ID: <7335613b-0a18-1c28-9b65-687d0b44d01f@linux.alibaba.com>
Date:   Wed, 15 Apr 2020 10:53:06 +0800
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On 2020/4/15 2:07, Ken Goldman wrote:
> I wonder if there's a different issue?? I just ran selftest with 
> fullTest = yes in two different TPM vendors.
> 
> One took 230 msec, the other 320 msec.
> 
> I've never seen anything near 10 seconds.
> 
> Note that this is worse than the worst case because it's forcing a full 
> retest.? The TPM typically starts its self test immediately at power up 
> and could be complete by the time the OS starts to boot.
> 
> When I run selftest with fullTest = no, I get 30 msec, probably
> because it's not doing anything.
> 
> On 4/14/2020 7:50 AM, Tianjia Zhang wrote:
>> Because ima_pcr_extend() to operate the TPM chip, this process is
>> very time-consuming, for IMA, this is a blocking action, especially
>> when the TPM is in self test state, this process will block for up
>> to ten seconds.
> 

Ten seconds is an extreme scenario, and I haven't seen this worst case, 
but the TPM driver will fail to return in this scenario.

Thanks and best,
Tianjia